It’s such a relief when you land at a new job and immediately feel at home. The boss is cool and nice and not strict about schedule, and your coworkers laugh at all your jokes. You’re comfortable, and that’s a good thing. But as Katie Douthwaite writes in a great Daily Muse post titled “5 Things You Shouldn’t Try to Get Away With at a New Job,” you shouldn’t get too comfortable. Douthwaite has held various management positions over the years, so she knows what she’s talking about. Read on to get her expert advice.

1. Bellyaching About Your Last Job — It’s always tempting to badmouth your last boss and/or set of coworkers. After all, they were a bunch of jerks! Fight the urge, though. Until your new colleagues really get to know you, they’re liable to take you for a complainer and a gossip—someone who’ll talk smack about them before too long.

2. Being Flexible With Schedule — Some offices are extremely lenient when it comes to start and stop times, breaks, lunches, and the like. Even if your bosses are super flexible, Douthwaite writes, you should come in on time or early and leave at the same time as everyone else—at least for a while. Then, once you have a sense of how often it’s OK to take advantage of the flexibility, you can begin doing so.

3. Being Super Sarcastic — People don’t always get sarcasm. Yeah, it’s your sense of humor and a big part of your personality, but do you want people to see you as harsh or disrespectful? Even if you’re neither of those things, you may seem like it if you let the sarcasm fly. Tone it down until people know you.

4. Judging Everyone — Man, that Susie in accounting does sloppy work. And Jimmy in sales never shuts up. But what if Susie is secretly brilliant? Perhaps Jimmy gives incredible presentations. You shouldn’t rush to judge your new group of coworkers. Give it some time, and once you’ve been there a while, you’ll know what people bring to the table and who you might want to work with on projects.

5. Challenging Authority — You’re liable to arrive with loads of ideas about how you can improve processes and make the company more efficient, and some of them might be great. The trouble is, as a newcomer, you don’t really understand problems well enough to solve them, and you might not have a sense of the boss’ communication style and how they prefer being approached about such things. In other words, Douthwaite says, you’re “simply complaining.”